fcolorbox c1 c2 text is like colorbox, with a frame of c1 around a box
of background colour c2.
For example, fcolorbox red green Text sets Text in the current text colour
on a green background with a red frame.

The two specifications must either both be defined ones, or both use the same
model, which is given only once, this limitation only make sense in LaTeX
parlance but is helpful here to understand why this function can fail.

normalcolor switches to the colour that was active at the end of the preamble.
Thus placing a color declaration in the preamble can change the standard colour
for the whole document. This is the equivalent to normalfont for font selection.